COSMIC RAYS AND PARTICLE PHYSICS

Transcription

1 COSMIC RAYS AND PARTICLE PHYSICS Fully updated for the second edition, this book introduces the growing and dynamic field of particle astrophysics. It provides an overview of high-energy nuclei, photons, and neutrinos, including their origins, their propagation in the cosmos, their detection at Earth, and their relation to each other. Coverage is expanded to include new content on high energy physics, the propagation of protons and nuclei in cosmic background radiation, neutrino astronomy, high-energy and ultra-high-energy cosmic rays, sources and acceleration mechanisms, and atmospheric muons and neutrinos. Readers are able to master the fundamentals of particle astrophysics within the context of the most recent developments in the field. This book will benefit graduate students and established researchers alike, equipping them with the knowledge and tools needed to design and interpret their own experiments and, ultimately, to address a number of questions concerning the nature and origins of cosmic particles that have arisen in recent research. THOMAS K. GAISSERis Martin A. Pomerantz Professor of Physics at the University of Delaware. He is a Fellow of the American Physical Society and recipient of the Alexander von Humboldt prize. His research at the Bartol Research institute in the Department of Physics and Astronomy includes cosmic-ray physics, atmospheric neutrinos, and neutrino astronomy. RALPH ENGEL is a senior scientist at the Karlsruhe Institute of Technology (KIT). He specializes in the application of high energy physics to problems in particle astrophysics, focusing on the physics and detection of high-energy and ultra-high-energy cosmic rays. He is an author of several simulation codes commonly applied in cosmic ray physics. ELISA RESCONI is a Heisenberg Professor of Physics at the Technical University Munich (TUM). Prof. Resconi s research focuses on experimental physics with cosmic particles at TUM s Physics Department and Cluster of Excellence Universe, and includes studies of neutrinos in both astrophysics and particle physics. Most noteworthy, Prof. Resconi has developed novel methods in the search for cosmic neutrinos and their astrophysical sources, and in the fundamental study of neutrino properties.

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3 COSMIC RAYS AND PARTICLE PHYSICS THOMAS K. GAISSER University of Delaware RALPH ENGEL Karlsruhe Institute of Technology ELISA RESCONI Technical University Munich

4 University Printing House, Cambridge CB2 8BS, United Kingdom Cambridge University Press is part of the University of Cambridge. It furthers the University s mission by disseminating knowledge in the pursuit of education, learning and research at the highest international levels of excellence. Information on this title: / c Cambridge University Press 2016 This publication is in copyright. Subject to statutory exception and to the provisions of relevant collective licensing agreements, no reproduction of any part may take place without the written permission of Cambridge University Press. First published 2016 Printed in the United Kingdom by TJ International Ltd, Padstow, Cornwall A catalogue record for this publication is available from the British Library. Library of Congress Cataloguing in Publication data Names: Gaisser, Thomas K., author. Engel, Ralph, 1965 author. Resconi, Elisa, 1971 author. Title: Cosmic rays and particle physics / Thomas K. Gaisser (University of Delaware), Ralph Engel (Karlsruhe Institute of Technology), Elisa Resconi (Technical University Munich). Description: Second edition. Cambridge, United Kingdom : Cambridge University Press, c 2016 Includes bibliographical references and index. Identifiers: LCCN ISBN ISBN Subjects: LCSH: Cosmic rays. Particles (Nuclear physics) Nuclear astrophysics. Classification: LCC QC485.G DDC /97223 dc23 LC record available at ISBN Hardback Cambridge University Press has no responsibility for the persistence or accuracy of URLs for external or third-party internet websites referred to in this publication, and does not guarantee that any content on such websites is, or will remain, accurate or appropriate.

5 Contents Preface to the first edition Preface to the second edition page xi xiii 1 Cosmic rays What are cosmic rays? Objective of this book Types of cosmic ray experiment Composition of cosmic rays Energy spectra Energy density of cosmic rays 10 2 Cosmic ray data Lessons from the heliosphere Measurements with spectrometers Measurements with calorimeters Spectrum of all nucleons Indirect measurements at high energy Primary composition from air shower experiments 28 3 Particle physics Historical relation of cosmic ray and particle physics The Standard Model of particle physics Quark model of hadrons and hadron masses Oscillation of neutral mesons Electron positron annihilation Weak decays QCD-improved parton model and high-p K processes Concepts for describing low-p K processes 60 v

6 vi Contents 4 Hadronic interactions and accelerator data Basics Total and elastic cross sections Phenomenology of particle production Nuclear targets and projectiles Hadronic interaction of photons Extrapolation to very high energy Cascade equations Basic equation and boundary conditions Boundary conditions Energy loss by charged particles Electrons, positrons and photons Nucleons in the atmosphere Hadrons in the atmosphere The atmosphere Meson fluxes Atmospheric muons and neutrinos Meson decay Production of muons and muon neutrinos Muons in the atmosphere Relation to primary energy Muon charge ratio Neutrinos in the atmosphere Non-power law primary spectrum and scaling violations Neutrino masses and oscillations Neutrino mixing Oscillation in vacuum Oscillation in matter Neutrino mass hierarchy Oscillation over astronomical distances Muons and neutrinos underground Passage of muons through matter Atmospheric muons underground Neutrinos underground Prompt leptons Seasonal variation of atmospheric muons and neutrinos 183

7 Contents vii 9 Cosmic rays in the Galaxy Cosmic ray transport in the Galaxy The Galaxy Models of propagation Extragalactic propagation of cosmic rays Energy loss for protons and neutrons Photodisintegration of nuclei Secondary particle production The role of magnetic fields Astrophysical γ -rays and neutrinos γ -rays from decay of π Production of gamma rays by electron bremsstrahlung Diffuse γ -rays from the Galactic plane Neutrinos from the Galactic plane Spectrum of electrons Positrons Cosmic rays and γ -rays in external galaxies Acceleration Power Shock acceleration Acceleration at supernova blast waves Nonlinear shock acceleration The knee of the cosmic ray spectrum Acceleration to higher energy Supernovae in the Milky Way The Milky Way galaxy Supernovae The compact remnant: neutron stars and black holes High-energy binary systems Supernova remnants Pulsar wind nebulae Examples of supernova remnants Astrophysical accelerators and beam dumps Radiative processes in beam dumps Active galactic nuclei Gamma ray bursts 295

8 viii Contents 15 Electromagnetic cascades Basic features of cascades Analytic solutions in cascade theory Approximations for total number of particles Fluctuations Lateral spread Extensive air showers Basic features of air showers The Heitler Matthews splitting model Muons in air showers Nuclei and the superposition model Elongation rate theorem Shower universality and cross section measurement Particle detector arrays Atmospheric Cherenkov light detectors Fluorescence telescopes Radio signal detection Very high energy cosmic rays The knee of the spectrum Depth of shower maximum and composition Ultra-high-energy cosmic rays Sources of extragalactic cosmic rays Future experiments Neutrino astronomy Motivation for a kilometer-scale neutrino telescope From DUMAND to IceCube and beyond Signals and backgrounds in a neutrino detector Event types Searching for point sources of neutrinos Observation of astrophysical neutrinos Sources of astrophysical neutrinos Multi-messenger astronomy 372 Appendix 374 A.1 Units, constants and definitions 374 A.2 References to flux measurements 374 A.3 Particle flux, density and interaction cross section 375 A.4 Fundamentals of scattering theory 378

9 Contents ix A.5 Regge amplitude 384 A.6 Glauber model of nuclear cross sections 386 A.7 Earth s atmosphere 390 A.8 Longitudinal development of air showers 391 A.9 Secondary positrons and electrons 393 A.10 Liouville s theorem and cosmic ray propagation 395 A.11 Cosmology and distance measures 397 A.12 The Hillas splitting algorithm 399 References 402 Index 441

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11 Preface to the first edition The connection between cosmic rays and particle physics has experienced a renewal of interest in the past decade. Large detectors, deep underground, sample groups of coincident cosmic ray muons and study atmospheric neutrinos while searching for proton decay, monopoles, neutrino oscillations, etc. Detector arrays at the surface measure atmospheric cascades in the effort to identify sources of the most energetic naturally occurring particles. This book is an introduction to the phenomenology and theoretical background of this field of particle astrophysics. The book is directed to graduate students and researchers, both experimentalists and theorists, with an interest in this growing interdisciplinary field. The book is divided into an introductory section and three main parts. The two introductory chapters give a brief background of cosmic ray physics and particle physics. Chapters 5 through 8 concern cosmic rays in the atmosphere hadrons, photons, muons and neutrinos. The second major part (chapters 9 13) is about propagation, acceleration and origin of cosmic rays in the galaxy. Air showers and related topics are the subject of the last four chapters. I am grateful to many colleagues at Bartol and elsewhere for discussions which have helped me learn about aspects of the field. I thank Alan Watson, Raymond Protheroe, Paolo Lipari, Francis Halzen, David Seckel, Todor Stanev, Floyd Stecker and Carl Fichtel for reading various chapters and offering helpful suggestions. I thank Leslie Hodson, Jack van der Velde, Jay Perrett and Sergio Petrera for providing me with photographs to illustrate the book. xi

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13 Preface to the second edition Interest and activity in particle astrophysics has continued to grow. It has now been 25 years since publication of the first edition. A new edition is long overdue, but nevertheless well-motivated in view of the growth of the field and several important discoveries in the interim. The discoveries include flavor oscillations in atmospheric and solar neutrinos, the cutoff of the spectrum of ultra-high-energy cosmic rays, TeV gamma rays from supernova remnants in the Galaxy and from distant active galaxies, an unexpected excess of positrons at high energy (but not of anti-protons) and, most recently, high-energy astrophysical neutrinos. The discoveries are the result of major investments in the development of new instruments: the major underground experiments, Super-Kamiokande, SNO and Borexino; the giant air shower arrays, Auger and Telescope Array; the imaging atmospheric Cherenkov telescopes VERITAS, H.E.S.S. and MAGIC, and the Fermi Satellite; the particle spectrometers in space, PAMELA and AMS-02, along with balloon-borne detectors ATIC and CREAM; and the neutrino telescopes AMANDA and Baikal, ANTARES and IceCube. Corresponding developments on the side of particle physics stem from the colliding beam machines at DESY, Fermilab and CERN. These have provided measurements of parton distribution functions over an unprecedented kinematic range, the discovery of the top quark and, most recently, the discovery of the Higgs boson. The LHC is now running at a center of mass energy equivalent to ev in the lab, well above the knee in the cosmic ray spectrum. All of the discoveries mentioned have given rise to new questions that stimulate continuing interest in particle astrophysics. In writing this expanded edition, we have kept the basic structure of the first edition while adding chapters on new topics stimulated by some of these open questions. Topics of the new chapters include neutrino oscillations, propagation of ultra-high energy cosmic rays in the cosmic microwave background, sources of the highest energy cosmic rays and neutrino xiii

14 xiv Preface to the second edition astronomy. The chapters on atmospheric muons and neutrinos, and those on acceleration and propagation of cosmic rays, go into greater depth and focus on new results. Most important are the two chapters on particle physics, which are completely new, and are intended to bring the latest results from high-energy physics to bear on cosmic ray physics. We are grateful to many colleagues who, in one way or another, helped us to understand and explain the material in this book.